[Development] Proposal to raise the minimum CMake version needed to build and use Qt 6.9

[Alexandru Croitor]

Hi,

We'd like to bump the minimum required CMake version for building and using Qt to CMake 3.26.

The pending change is https://codereview.qt-project.org/c/qt/qtbase/+/603886

The rationale is easier maintenance of build system code, and allowing to provide better public cmake apis and behaviors 
(cleaner qml module apis, better deployment handling, better android handling, better static linking handling, to name a few).

The timing is good because Qt 6.9 is non-LTS.

More context on the proposed version can be found at https://bugreports.qt.io/browse/QTBUG-131169

If you have some feedback on why that might be a problem, please reach out.

Alexandru.